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Justus, C. G.

Publications and source records attributed to Justus, C. G..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Mars Global Reference Atmospheric Model (Mars-GRAM) Version 3.8: Users Guide

Mars Global Reference Atmospheric Model (Mars-GRAM) Version 3.8 is presented and its new features are discussed. Mars-GRAM uses new values of planetary reference ellipsoid radii, gravity term, and rotation rate (consistent with current JPL values) and includes centrifugal effects on gravity. The model now uses NASA Ames Global Circulation Model low resolution topography. Curvature corrections are applied to winds and limits based on speed of sound are applied. Altitude of the F1 ionization peak and density scale height, including effects of change of molecular weight with altitude are computed. A check is performed to disallow temperatures below CO2 sublimination. This memorandum includes instructions on obtaining Mars-GRAM source code and data files and running the program. Sample input and output are provided. An example of incorporating Mars-GRAM as an atmospheric subroutine in a trajectory code is also given.

Justus, C. G.↗
NASA NTRS1996

A Revised Thermosphere for the Mars Global Reference Atmospheric Model (Mars-GRAM Version 3.4)

This report describes the newly-revised model thermosphere for the Mars Global Reference Atmospheric Model (Mars-GRAM, Version 3.4). It also provides descriptions of other changes made to the program since publication of the programmer's guide for Mars-GRAM Version 3.34. The original Mars-GRAM model thermosphere was based on the global-mean model of Stewart. The revised thermosphere is based largely on parameterizations derived from output data from the three-dimensional Mars Thermospheric Global Circulation Model (MTGCM). The new thermospheric model includes revised dependence on the 10.7 cm solar flux for the global means of exospheric temperature, temperature of the base of the thermosphere, and scale height for the thermospheric temperature variations, as well as revised dependence on orbital position for global mean height of the base of the thermosphere. Other features of the new thermospheric model are: (1) realistic variations of temperature and density with latitude and time of day, (2) more realistic wind magnitudes, based on improved estimates of horizontal pressure gradients, and (3) allowance for user-input adjustments to the model values for mean exospheric temperature and for height and temperature at the base of the thermosphere. Other new features of Mars-GRAM 3.4 include: (1) allowance for user-input values of climatic adjustment factors for temperature profiles from the surface to 75 km, and (2) a revised method for computing the sub-solar longitude position in the 'ORBIT' subroutine.

Justus, C. G.↗
NASA NTRS1996

Mars Global Reference Atmospheric Model (Mars-GRAM 3.34): Programmer's Guide

This is a programmer's guide for the Mars Global Reference Atmospheric Model (Mars-GRAM 3.34). Included are a brief history and review of the model since its origin in 1988 and a technical discussion of recent additions and modifications. Examples of how to run both the interactive and batch (subroutine) forms are presented. Instructions are provided on how to customize output of the model for various parameters of the Mars atmosphere. Detailed descriptions are given of the main driver programs, subroutines, and associated computational methods. Lists and descriptions include input, output, and local variables in the programs. These descriptions give a summary of program steps and 'map' of calling relationships among the subroutines. Definitions are provided for the variables passed between subroutines through common lists. Explanations are provided for all diagnostic and progress messages generated during execution of the program. A brief outline of future plans for Mars-GRAM is also presented.

Justus, C. G.↗
NASA NTRS1995

The NASA/MSFC Global Reference Atmospheric Model-1995 version (GRAM-95)

The latest version of the Global Reference Atmospheric Model (GRAM-95) is presented and discussed. GRAM-95 uses the new Global Upper Air Climatic Atlas (GUACA) CD-ROM data set, for 0- to 27-km altitudes. As with earlier versions, GRAM-95 provides complete geographical and altitude coverage for each month of the year. Individual years 1985 to 1991 and a period-of-record (1980 to 1991) can be simulated for the GUACA height range. GRAM-95 uses a specially developed data set, based on Middle Atmosphere Program (MAP) data, for the 20- to 120-km height range, and the NASA Marshall Engineering Thermosphere (MET) model for heights above 90 km. Fairing techniques assure a smooth transition in the overlap height ranges (20 to 27 km and 90 to 120 km). In addition to the traditional GRAM variables of pressure, density, temperature and wind components, GRAM-95 now includes water vapor and 11 other atmospheric constituents (O3, N2O, CO, CH4, CO2, N2, O2, O, A, He, and H). A new, variable-scale perturbation model provides both large-scale and small-scale deviations from mean values for the thermodynamic variables and horizontal and vertical wind components. The perturbation model includes new features that simulate intermittency (patchiness) in turbulence and small-scale perturbation fields. The density perturbations and density gradients (density shears) computed by the new model compare favorably in their statistical characteristics with observed density perturbations and density shears from 32 space shuttle reentry profiles. GRAM-95 provides considerable improvement in wind estimates from the new GUACA data set, compared to winds calculated from the geostrophic wind relations previously used in the 0- to 25-km height range. The GRAM-95 code has been put into a more modular form, easier to incorporate as subroutines in other programs (e.g., trajectory codes). A complete user's guide for running the program, plus sample input and output, is provided.

Justus, C. G.↗
NASA NTRS1994

A rapid radiative transfer model for reflection of solar radiation

A rapid analytical radiative transfer model for reflection of solar radiation in plane-parallel atmospheres is developed based on the Sobolev approach and the delta function transformation technique. A distinct advantage of this model over alternative two-stream solutions is that in addition to yielding the irradiance components, which turn out to be mathematically equivalent to the delta-Eddington approximation, the radiance field can also be expanded in a mathematically consistent fashion. Tests with the model against a more precise multistream discrete ordinate model over a wide range of input parameters demonstrate that the new approximate method typically produces average radiance differences of less than 5%, with worst average differences of approximately 10%-15%. By the same token, the computational speed of the new model is some tens to thousands times faster than that of the more precise model when its stream resolution is set to generate precise calculations.

Xiang, X.↗
NASA NTRS1993

Global Reference Atmospheric Model - 1990

GRAM-90, improvement on original model, provides values of atmospheric parameters, either automatically at positions along linear path or along any set of connected positions specified by user. Parameters produced include monthly total and mean values of pressure, density, temperature, and wind, as well as perturbation values and magnitudes. Also provides thermal wind shear for monthly mean winds, percent deviation from standard atmosphere, mean vertical wind, and perturbation data for each position. Perturbation data consist of values of quasi-biennial and random perturbations. Written in FORTRAN 77.

Justus, C. G.↗
NASA NTRS1993

Global Reference Atmosphere Model (GRAM)

4D model provides atmospheric parameter values either automatically at positions along linear path or along any set of connected positions specified by user. Based on actual data, GRAM provides thermal wind shear for monthly mean winds, percent deviation from standard atmosphere, mean vertical wind, and perturbation data for each position.

Johnson, D. L.↗
NASA NTRS1992

Additions to Mars Global Reference Atmospheric Model (MARS-GRAM)

Three major additions or modifications were made to the Mars Global Reference Atmospheric Model (Mars-GRAM): (1) in addition to the interactive version, a new batch version is available, which uses NAMELIST input, and is completely modular, so that the main driver program can easily be replaced by any calling program, such as a trajectory simulation program; (2) both the interactive and batch versions now have an option for treating local-scale dust storm effects, rather than just the global-scale dust storms in the original Mars-GRAM; and (3) the Zurek wave perturbation model was added, to simulate the effects of tidal perturbations, in addition to the random (mountain wave) perturbation model of the original Mars-GRAM. A minor modification was also made which allows heights to go 'below' local terrain height and return 'realistic' pressure, density, and temperature, and not the surface values, as returned by the original Mars-GRAM. This feature will allow simulations of Mars rover paths which might go into local 'valley' areas which lie below the average height of the present, rather coarse-resolution, terrain height data used by Mars-GRAM. Sample input and output of both the interactive and batch versions of Mars-GRAM are presented.

Justus, C. G.↗
NASA NTRS1992

Mars global reference atmosphere model (Mars-GRAM)

Mars-GRAM is an empirical model that parameterizes the temperature, pressure, density, and wind structure of the Martian atmosphere from the surface through thermospheric altitudes. In the lower atmosphere of Mars, the model is built around parameterizations of height, latitudinal, longitudinal, and seasonal variations of temperature determined from a survey of published measurements from the Mariner and Viking programs. Pressure and density are inferred from the temperature by making use of the hydrostatic and perfect gas laws relationships. For the upper atmosphere, the thermospheric model of Stewart is used. A hydrostatic interpolation routine is used to insure a smooth transition from the lower portion of the model to the Stewart thermospheric model. Other aspects of the model are discussed.

Justus, C. G.↗
NASA NTRS1991

Additions to Mars Global Reference Atmospheric Model (Mars-GRAM)

Three major additions or modifications were made to the Mars Global Reference Atmospheric Model (Mars-GRAM): (1) in addition to the interactive version, a new batch version is available, which uses NAMELIST input, and is completely modular, so that the main driver program can easily be replaced by any calling program, such as a trajectory simulation program; (2) both the interactive and batch versions now have an option for treating local-scale dust storm effects, rather than just the global-scale dust storms in the original Mars-GRAM; and (3) the Zurek wave perturbation model was added, to simulate the effects of tidal perturbations, in addition to the random (mountain wave) perturbation model of the original Mars-GRAM. A minor modification has also been made which allows heights to go below local terrain height and return realistic pressure, density, and temperature (not the surface values) as returned by the original Mars-GRAM. This feature will allow simulations of Mars rover paths which might go into local valley areas which lie below the average height of the present, rather coarse-resolution, terrain height data used by Mars-GRAM. Sample input and output of both the interactive and batch version of Mars-GRAM are presented.

Justus, C. G.↗
NASA NTRS1991

The NASA/MSFC global reference atmospheric model: 1990 version (GRAM-90). Part 2: Program/data listings

A new (1990) version of the NASA/MSFC Global Reference Atmospheric Model (GRAM-90) was completed and the program and key data base listing are presented. GRAM-90 incorporate extensive new data, mostly collected under the Middle Atmosphere Program, to produce a completely revised middle atmosphere model (20 to 120 km). At altitudes greater than 120 km, GRAM-90 uses the NASA Marshall Engineering Thermosphere model. Complete listings of all program and major data bases are presented. Also, a test case is included.

Justus, C. G.↗
NASA NTRS1991

The NASA/MSFC global reference atmospheric model: 1990 version (GRAM-90). Part 1: Technical/users manual

A technical description of the NASA/MSFC Global Reference Atmospheric Model 1990 version (GRAM-90) is presented with emphasis on the additions and new user's manual descriptions of the program operation aspects of the revised model. Some sample results for the new middle atmosphere section and comparisons with results from a three dimensional circulation model are provided. A programmer's manual with more details for those wishing to make their own GRAM program adaptations is also presented.

Justus, C. G.↗
NASA NTRS1991

Global Reference Atmosphere Model-1988

Four-D Global Reference Atmosphere computer program (GRAM) developed from empirical mathematical model of atmosphere generating values for pressure, density, temperature, and winds from surface level to orbital altitudes. Generates altitude profiles of parameters of atmosphere along any simulated trajectory through atmosphere. Developed from design applications in Space Shuttle program. Other potential applications include studies of global circulation and diffusion and generation of profiles for comparison with results of other atmospheric-measurement techniques such as satellite-measured temperature profiles and wind profiles from infrasonic measurements. Written in STANDARD FORTRAN 77.

Johnson, D. L.↗
NASA NTRS1990

New Atmospheric Turbulence Model for Shuttle Applications

An updated NASA atmospheric turbulence model, from 0 to 200 km altitude, which was developed to be more realistic and less conservative when applied to space shuttle reentry engineering simulation studies involving control system fuel expenditures is presented. The prior model used extreme turbulence (3 sigma) for all altitudes, whereas in reality severe turbulence is patchy within quiescent atmospheric zones. The updated turublence model presented is designed to be more realistic. The prior turbulence statistics (sigma and L) were updated and were modeled accordingly.

Justus, C. G.↗
NASA NTRS1990

Extensive middle atmosphere (20-120 KM) modification in the Global Reference Atmospheric Model (GRAM-90)

The Global Reference Atmospheric Model (GRAM) is currently available in the 'GRAM-88' version (Justus, et al., 1986; 1988), which includes relatively minor upgrades and changes from the 'MOD-3' version (Justus, et al., 1980). Currently a project is underway to use large amounts of data, mostly collected under the Middle Atmosphere Program (MAP) to produce a major upgrade of the program planned for release as the GRAM-90 version. The new data and program revisions will particularly affect the 25-90 km height range. Sources of data and preliminary results are described here in the form of cross-sectional plots.

Justus, C. G.↗
NASA NTRS1988

Development of an engineering model atmosphere for Mars

An engineering model atmosphere for Mars is being developed with many of the same features and capabilities for the highly successful Global Reference Atmospheric Model (GRAM) program for Earth's atmosphere. As an initial approach, the model is being built around the Martian atmosphere model computer subroutine (ATMOS) of Culp and Stewart (1984). In a longer-term program of research, additional refinements and modifications will be included. ATMOS includes parameterizations to stimulate the effects of solar activity, seasonal variation, diurnal variation magnitude, dust storm effects, and effects due to the orbital position of Mars. One of the current shortcomings of ATMOS is the neglect of surface variation effects. The longer-term period of research and model building is to address some of these problem areas and provide further improvements in the model (including improved representation of near-surface variations, improved latitude-longitude gradient representation, effects of the large annual variation in surface pressure because of differential condensation/sublimation of the CO2 atmosphere in the polar caps, and effects of Martian atmospheric wave perturbations on the magnitude of the expected density perturbation.

Justus, C. G.↗